[PATCH v2] nvme-core: initialize status to NVME_SC_HOST_PATH_ERROR

[Keith Busch]

On Thu, Apr 15, 2021 at 12:30:30PM -0700, Keith Busch wrote:
> On Wed, Apr 14, 2021 at 11:08:33AM -0600, Yuanyuan Zhong wrote:
> > Block layer blk_end_sync_rq() silently drops blk_status_t error.
> > When ->queue_rq returns error, nvme driver should set nvme status
> > explicitly. Otherwise the passthrough command may take the stale
> > status as result. A typical value zero will be interpreted as
> > NVME_SC_SUCCESS, despite the dispatching error from ->queue_rq.
> > 
> > Instead of trying to fix it for every error return, this change
> > initialize the status to NVME_SC_HOST_PATH_ERROR during
> > nvme_clear_nvme_request().
> 
> It doesn't look like these types of errors are unique to nvme. Could we
> not just have blk_execute_rq() return an error instead?

The following enables all callers to know if queue_rq() failed:

---
diff --git a/block/blk-exec.c b/block/blk-exec.c
index beae70a0e5e5..6d12524a91f9 100644
--- a/block/blk-exec.c
+++ b/block/blk-exec.c
@@ -21,7 +21,7 @@ static void blk_end_sync_rq(struct request *rq, blk_status_t error)
 {
 	struct completion *waiting = rq->end_io_data;
 
-	rq->end_io_data = NULL;
+	rq->end_io_data = ERR_PTR(blk_status_to_errno(error));
 
 	/*
 	 * complete last, if this is a stack request the process (and thus
@@ -73,7 +73,7 @@ EXPORT_SYMBOL_GPL(blk_execute_rq_nowait);
  *    Insert a fully prepared request at the back of the I/O scheduler queue
  *    for execution and wait for completion.
  */
-void blk_execute_rq(struct gendisk *bd_disk, struct request *rq, int at_head)
+int blk_execute_rq(struct gendisk *bd_disk, struct request *rq, int at_head)
 {
 	DECLARE_COMPLETION_ONSTACK(wait);
 	unsigned long hang_check;
@@ -87,5 +87,6 @@ void blk_execute_rq(struct gendisk *bd_disk, struct request *rq, int at_head)
 		while (!wait_for_completion_io_timeout(&wait, hang_check * (HZ/2)));
 	else
 		wait_for_completion_io(&wait);
+	return PTR_ERR_OR_ZERO(rq->end_io_data);
 }
 EXPORT_SYMBOL(blk_execute_rq);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 1a6f89d1110c..9ed540d168af 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -933,7 +933,7 @@ extern int blk_rq_map_kern(struct request_queue *, struct request *, void *, uns
 extern int blk_rq_map_user_iov(struct request_queue *, struct request *,
 			       struct rq_map_data *, const struct iov_iter *,
 			       gfp_t);
-extern void blk_execute_rq(struct gendisk *, struct request *, int);
+extern int blk_execute_rq(struct gendisk *, struct request *, int);
 extern void blk_execute_rq_nowait(struct gendisk *,
 				  struct request *, int, rq_end_io_fn *);
 
--